BOSTON – An acting chief probation officer in Western Massachusetts was arrested and charged with intimidating and harassing another probation officer who is a witness in the federal investigation of hiring practices at the state Probation Department, the U.S. Attorney’s office said.

Christopher J. Hoffman, 39, of Hatfield, the acting chief probation officer in Hampshire Superior Court who was placed on leave on Oct. 26, is the first person to face criminal charges in the federal investigation of the probation department. Hoffman was charged in a criminal complaint with two counts of obstruction of justice, according to Massachusetts U.S. Attorney Carmen M. Ortiz.

The investigation has prompted the resignation of former commissioner John J. O’Brien, of Quincy. O’Brien has been indicted by a state grand jury on a charge of conspiracy to use unlawful means to get his wife a job at the state Lottery.

Hoffman’s arrest came 13 months after an independent investigator, Boston lawyer Paul F. Ware Jr., issued a sweeping report that detailed patronage and fraudulent hiring in the Probation Department, sparking state and federal investigations. Ware’s report said hiring was tilted in favor of connected applicants, including people recommended by judges and legislators. Officials in probation held many interviews for certain jobs, helping leave the impression of a transparent and objective hiring process.

Amid the federal investigation, Hoffman is charged with telling a probation officer whom he supervised, “I’m going to tell everyone that you are a rat.”

During an appearance in Worcester before U.S. District Court Judge Timothy S. Hillman, Hoffman was released on several conditions requested by the prosecution including one to have no contact with state Rep. Thomas M. Petrolati, a Ludlow Democrat known for recommending people who were hired by the probation department. Hoffman also must stay away from any current or former members of the state probation department. Hoffman was released on unsecured bond.

Hoffman is scheduled for a probable cause hearing on Jan. 24 in Worcester.

A spokeswoman for the U.S. attorney in Boston would not comment on why Hoffman was ordered to have no contact with Petrolati or his family members. Bongiorni said the complaint against Hoffman had nothing to do with Petrolati and that the no-contact order for Petrolati didn’t mean much.

“He does not have any contact with Mr. Petrolati in any event,” Bongiorni said.

House Speaker Robert A. DeLeo demoted Petrolati this year from his prior No. 3 position of power in the state House of Representatives to regular rank and file committee posts. Petrolati had agreed to give up the post in advance of his official demotion.

John P. Pucci, a Northampton lawyer representing Petrolati, said no evidence has surfaced that suggests Petrolati took part in any illegal behavior.

As a matter of constituent service, Petrolati made recommendations for people to get jobs, but that is not a crime, Pucci said. Many other members of the state Legislature also recommended people for positions in probation, he said.

The complaint alleges that on Oct. 18 and 19, Hoffman – in his capacity acting chief probation officer of the Hampshire Superior Court in Northampton – made threatening and intimidating remarks to Maureen Adams, a probation officer under his supervision.

On Oct. 19, Adams was scheduled to be interviewed by the FBI in connection with the federal investigation into the alleged fraudulent hiring practices at the state probation department, the U.S. Attorney’s office said in a press release.

Adams told Hoffman about her impending interview because it required her absence from work. It is alleged that Hoffman’s remarks included statements to the effect of: “I’m going to tell everyone that you are a rat.”

Hoffman also allegedly made misleading statements regarding his relationship with retired Deputy Commissioner of Probation William H. Burke III, of Hatfield, a press release said. In court, Hoffman was also ordered to have no contact with Burke or his family.

Hoffman told Adams that he only knew Burke because he grew up with him in Hatfield and that he called him “Mr. Burke,” according to an affidavit by a special FBI agent. Adams believed those statements were false and were made so she would repeat them to the FBI, the affidavit said.

Looking and sounding upset, Adams met with the FBI as scheduled at Friendly’s Restaurant in Northampton, the affidavit said.

If convicted, Hoffman faces up to 20 years in prison, to be followed by three years of supervised release and a $250,000 fine for intimidating a witness. Hoffman faces up to three years in prison, to be followed by one year of supervised release and a $250,000 fine for harassment of a witness, the release said.

Hoffman started as an associate probation officer in 2001 and became a probation officer in 2004. In 2008, he was promoted to acting assistant chief probation officer in Greenfield District Court. In 2009, he was promoted to acting chief in Northampton.

Ortiz and Richard DesLauriers, special agent in charge of the FBI in Boston, made the announcement about Hoffman’s arrest on Wednesday.

Coria Holland, a spokeswoman for the state probation department, issued a statement saying the Trial Court has just received a copy of the complaint against Hoffman and is in the process of changing Hoffman’s status from leave with pay to leave without pay consistent with trial court personnel policies. Hoffman’s salary was $73,170.50.

Attorney General Martha M. Coakley has said her office has an active and ongoing investigation that recently resulted in indictments against the former probation commissioner.

In September, Coakley announced indictments of former commissioner O’Brien, and the chief of staff to former state Treasurer Timothy P. Cahill, on charges they conspired to organize a campaign fund-raiser for Cahill in 2005 in exchange for getting O’Brien’s wife a job at the state Lottery.

Former deputy commissioner Burke and others were blunt in admitting that fixing interviews meant that less qualified candidates were hired or promoted over more qualified candidates in probation, the Ware report said.

Burke testified that the hiring and promotion was manipulated by the former commissioner in exchange for favorable action on the department’s budget, the report said.